A semiconductor laser typically comprises a body of semiconductor material, generally Group III-V compounds and alloys of such compounds, having a thin active layer between layers of opposite conductivity type. Constricted heterostructure semiconductor lasers, such as those disclosed by Botez in U.S. Pat. No. 4,347,486 and by Connolly et al in U.S. Pat. No. 4,461,008 and entitled, TERRACED HETEROSTRUCTURE SEMICONDUCTOR LASER, which are incorporated herein by reference, are capable of producing a single transverse (the direction perpendicular to the plane of the layers) and lateral (the direction in the plane of the layers and perpendicular to the direction of light propagation) mode, high-power laser beam. Light generated in the active layer of such devices is coupled into an adjacent guide layer and propagates in the active and the guide layer, thereby producing a much larger mirror facet area from which light is emitted. While the emitting area is larger than that for the conventional laser, this area is still typically only on the order of several square micrometers (.mu.m) at the mirror facet. The local power density is thus high and may result in damage to the mirror facet. To avoid facet damage the laser output power density at the facet is held below the threshold at which such damage occurs. In addition a transparent coating, such as that disclosed by Ladany et al. in U.S. Pat. No. 4,178,564, incorporated herein by reference, may be placed on the emitting facet to increase the threshold at which the damage occurs. This combination of measures reduces the incidence of facet damage but at the price of limiting the maximum output power of the laser to less than its inherent capability.
It has been suggested that catastrophic damage is caused by local heating of the facet to its melting temperature due to absorption of the laser light. To reduce or eliminate this effect, semiconductor lasers have been fabricated in which the light absorbing active layer of the device does not extend to the facets. The regions between the ends of the active layer and the facets are formed of a light transmissive material, thereby eliminating the problem of absorption at the facets. Such devices have shown a significant increase in the threshold powers at which long term and catastrophic damage occur of between about five and ten times.
Such devices do not, however, provide lateral mode control, particularly in the region adjacent to the facets and they require a two-step growth procedure with an intervening etching step. It would be desirable to have a constricted heterostructure semiconductor laser having lateral mode control extending to a non-absorbing mirror as well as to fabricate the laser in a one step growth process.